1. Field of the Invention
The present invention relates to an optical reader for reading recorded code data, an optical reading method and an optical reading system, and particularly relates to a technique for determining the stability of reading activity and predicting a change of reading performance.
2. Description of the Related Art
Heretofore, an optical reader for reading a label on which code data is recorded one-dimensionally such as a bar code reader is normally provided with a laser beam emitting circuit for emitting a laser beam, scanning means for attaching a polygon mirror to a rotating shaft and rotating the polygon mirror by a motor or the like and a light receiving element for generating an electric signal by receiving a laser beam reflected from a bar code to be read, and the code data of the bar code is detected by scanning a laser beam output from the laser beam emitting circuit on the bar code by the scanning means and decoding a signal output from the light receiving element.
Recently, a two-dimensional code in which the recordable quantity of information can be greatly increased and code data is two-dimensionally recorded has been developed in place of the above bar code. To read the code data of the two dimensional code, an optical reader using an image sensing device for example is used.
In the above optical reader, a reading error may occur and a reading speed may be deteriorated due to the contamination of a recorded code, the change of density and a failure of formation when a code is printed or marked, the existence of disturbed light, the contamination of a polygon mirror and a light emitting section of the optical reader or the like. Therefore, it is known that fixed reading stability cannot be acquired for a long term.
The stability of reading is the most important factor for such an optical reader and a device for supplementarily outputting an index to evaluate the stability of reading has been made heretofore.
For the index of the stability of reading, the frequency of reading trials (scanned frequency), the frequency of successful reading, the combination of these indexes or the like can be given. Then, a technique for providing reading stability verification means for outputting these indexes as supplementary information and judging a state in which a code is recorded is known.
However, the verification of the above conventional type stability of reading is the evaluation determined based upon only a threshold of whether reading is successful or not and when it is determined that reading is successful, it is not evaluated how the stability of reading is when the reading is successful. Therefore, if reading is continued as it is, it is difficult to grasp whether the result of reading is normal or not.
For example, if the recording density of a bar code label or the like becomes faint as time goes or if dust and contamination are gradually deposited on a light emitting section and the like of the optical reader, reading is normally performed in the initial operation of the optical reader, stability is gradually deteriorated and finally, reading may be disabled. In such a case, a situation that an error suddenly occurs without previous notice during reading in the conventional optical reader occurs.
When such a situation occurs, the whole system is required to be once stopped and to be maintained in a system to which the optical reader is connected and if the optical reader is used for a manufacturing line, great deal of loss time occurs and the manufacturing cost is increased.
The present invention is provided to solve such problems and an object t thereof is to provide an optical reader, an optical reading method and an optical reading system which can respectively cope before a state that reading is disabled occurs by always determining how the stability of reading is even if reading of code data is enabled and outputting a signal.
To achieve the above object, according to a first aspect of the present invention, there is provided an optical reader for optically reading recorded code data and determining whether the reading is successful or not, comprising: a light emitting means for emitting light to an object having code data; a light receiving means for receiving the light reflected on the code data of the object; and a stability determination means for comparing a frequency of coincidence of read code data from start of reading with a predetermined reference frequency when it is determined that the reading is successful after the reading of the code data is repeatedly tried, determining a stability of reading and outputting a signal showing a result of the determination.
According to a second aspect of the present invention, there is provided an optical reader for optically reading recorded code data and determining whether the reading is successful or not, comprising: a light emitting means for emitting light to an object having code data; a light receiving means for receiving the light reflected on the code data of the object; and a stability determination means for comparing time which elapses from start of reading until read data is coincided by a predetermined frequency with predetermined reference time when it is determined that the reading is successful after the reading of the code data is repeatedly tried, determining a stability of reading and outputting a signal showing a result of the determination.
According to a third aspect of the present invention, there is provided an optical reading system for optically reading recorded code data and determining whether the reading is successful or not, comprising: an optical reading means comprising a light emitting means for emitting light to an object having code data, and a light receiving means for receiving the light reflected on the code data of the object; a stability determination means for comparing a frequency of coincidence of read code data from start of reading with a predetermined reference frequency when it is determined that the reading is successful after the reading of the code data is repeatedly tried, determining a stability of reading and outputting a signal showing a result of the determination; and a control means for inputting the output signal of the stability determination means.
According to a fourth aspect of the present invention, there is provided an optical reading method comprising the steps of: optically reading recorded code data of an object; determining whether the reading is successful or not, wherein when the reading of the code data is carried out, the reading activity is done repeatedly; comparing a frequency of coincidence of read data from start of reading with a predetermined reference frequency; determining a result of stability of reading based on the comparison when the reading is successful; and outputting an output signal indicating the result of the determination.
According to a fifth aspect of the present invention, there is provided an optical reading method comprising the steps of: optically reading recorded code data of an object by a plurality of optical reading devices; determining whether the reading is successful or not, wherein when the reading of the code data is carried out, the reading activity is done repeatedly; comparing a frequency of coincidence of read data from start of reading with a predetermined reference frequency; determining a result of stability of reading based on the comparison when the reading is successful, wherein when the result of determination that stability is low is output from a plurality of optical reading devices in reading the same data, it is determined that a specified code data is erroneous; and outputting an output signal indicating the result of the determination and the specified code data.
According to a sixth aspect of the present invention, there is provided an optical reading method comprising the steps of: optically reading recorded code data of an object by a plurality of optical reading devices; determining whether the reading is successful or not, wherein when the reading of the code data is carried out, the reading activity is done repeatedly; comparing a frequency of coincidence of read data from start of reading with a predetermined reference frequency; determining a result of stability of reading based on the comparison when the reading is successful, wherein when the result of determination that stability is low is output from the same optical reading device irrespective of code data, it is determined that the same optical reading device fails; and outputting an output signal indicating the result of the determination and the same optical reading device.